Integrated optical service channel and quantum key distribution channel

1. An apparatus comprising: a first wavelength division (WDM) optical coupler having a first input configured to receive an output of an optical amplifier and a second input configured to receive an output from an optical service channel (OSC) transmitter, and configured to output a first optical signal containing OSC signals produced by the OSC transmitter in a first wavelength channel; and a second WDM optical coupler having a first input coupled to the output of the first WDM optical coupler and a second input coupled to an output of a quantum key distribution (QKD) transmitter, and configured to output to a single mode optical fiber the first optical signal in the first wavelength channel and at the same time a second optical signal containing QKD signals produced by the QKD transmitter in a second wavelength channel.

2. The apparatus of claim 1 , wherein the QKD transmitter is driven by a distributed feedback cooled laser.

3. A system comprising the apparatus of claim 1 , and further comprising a receiver apparatus configured to be coupled to an opposite end of the single mode optical fiber, wherein the receiver apparatus comprises a first WDM optical coupler, a second WDM optical coupler and a third WDM optical coupler, wherein an input of the first WDM optical coupler is configured to be coupled to the opposite end of the single mode optical fiber and an input of the second WDM optical coupler is configured to be coupled to a first output of the first WDM optical coupler and an input of the third WDM optical coupler is coupled to a second output of the first WDM optical coupler, wherein the first and third WDM optical couplers are configured to operate in the second wavelength channel and the first WDM optical coupler is configured to operate in the first wavelength channel, and further comprising a QKD receiver configured to connect to an output of the second WDM optical coupler and an OSC receiver configured to connect to a first output of the third WDM optical coupler, and wherein a second output of the third WDM optical coupler is configured to connect to an optical amplifier.

4. A system comprising the apparatus of claim 1 , and further comprising a receiver apparatus configured to be coupled to an opposite end of the single mode optical fiber, wherein the receiver apparatus comprises a first filter, a second filter and a WDM optical coupler, wherein an input of the first filter is configured to be coupled to the opposite end of the single mode optical fiber and an input of the second filter is configured to be coupled to a first output of the first filter and an input of the WDM optical coupler is coupled to a second output of the first filter, wherein the first and second filters have a pass band corresponding to the second wavelength channel and the WDM optical coupler is configured to operate in the first wavelength channel, and further comprising a QKD receiver configured to connect to an output of the second filter and an OSC receiver configured to connect to a first output of the WDM optical coupler, and wherein a second output of the WDM optical coupler is configured to connect to an optical amplifier.

5. A system comprising the apparatus of claim 1 , and further comprising a receiver apparatus configured to be coupled to an opposite end of the single mode optical fiber, wherein the receiver apparatus comprises an optical circulator having first, second and third ports, a first optical coupler and a second optical coupler, and a Fiber Bragg grating filter, the first port of the optical circulator being connected to the opposite end of the single mode fiber, the second port of the optical circulator being connected to the first optical coupler and the third port of the optical circulator being connected to the Fiber Bragg grating filter and an input of the second optical coupler being connected to an output of the Fiber Bragg grating filter, and further comprising a QKD receiver configured to connect to an output of the first optical coupler and an OSC receiver configured to connect to a first output of the second optical coupler.

6. An optical network comprising a plurality of nodes, a first node comprising the apparatus of claim 1 , wherein the plurality of nodes are connected to each other in a loop with the single mode optical fiber, and wherein the first node is configured to transmit optical signals in the first and second wavelength channels on the optical fiber along with first and second QKD keys to a second one of the plurality of nodes, and the second node drops the first wavelength channel and the first QKD key and regenerates the second QKD key for transmission to a third node in the loop and the third node is configured to drop the second QKD key and the second wavelength channel.

7. The optical network of claim 6 , wherein the first node is configured to assign the first and second QKD keys to a corresponding one of the first and second wavelength channels, and the first node is configured to transmit QKD key and wavelength information pertaining the assignment of the QKD keys to wavelength channels in an OSC via the OSC transmitter, and wherein the second node receives the QKD key and wavelength information, evaluates the QKD key and wavelength information for correctness to decide whether to use it locally or to forward it to a next node in the loop.

8. An optical network comprising: a plurality of nodes connected to each other in a loop with a single mode optical fiber; a first node configured to transmit optical signals in first and second wavelength channels on the optical fiber along with first and second quantum key distribution (QKD) keys to a second one of the plurality of nodes; the second node being configured to receive the first and second wavelength channels and the first and second QKD keys and to drop the first wavelength channel and the first QKD key and to regenerate the second QKD key for transmission to a third node in the loop; the third node being configured to drop the second QKD key and the second wavelength channel.

9. The optical network of claim 8 , wherein the first node is configured to assign one of the first and second QKD keys to a corresponding one of the first and second wavelength channels, and the first node is configured to transmit QKD key and wavelength information pertaining to assignment of QKD keys to wavelength channels in an optical service channel, and wherein the second node receives the QKD key and wavelength information, evaluates the QKD key and wavelength information for correctness to decide whether to use it locally or to forward it to a next node in the loop.

10. A method comprising: in an optical network comprising a plurality of nodes connected to each other in a loop with a single mode optical fiber; transmitting optical signals from a first node in first and second wavelength channels on the optical fiber together with first and second quantum key distribution (QKD) keys to a second node; receiving the first and second wavelength channels at a second node together with the first and second QKD keys; at the second node, dropping the first wavelength channel and the first QKD key at the second node and regenerating the second QKD key; transmitting the second wavelength channel and the second QKD key from the second node to a third node; and receiving the second QKD key at the third node and dropping the second QKD key and the second wavelength channel at the third node.

11. The method of claim 10 , where at the first node, further comprising assigning one of the first and second QKD keys to a corresponding one of the first and second wavelength channels, and wherein transmitting from the first node comprises transmitting QKD key and wavelength information pertaining to QKD key and wavelength assignment via an optical service channel over the single mode optical fiber, and wherein at the second node, further comprising receiving the QKD key and wavelength information and evaluating the QKD key and wavelength information for correctness to decide whether to use it locally or to forward it to a next node in the loop.